Spring scale



March 1, 19.32. s, AVERELL SPRING SCALE Filed June 6, 1929 llllllllllllllllllllll l\ m I I I INVENTOR. Sylvester Gfl verell TORNE';%.

Patented Mar. 1, 1932 PAT NT FFICE SYLVESTER- G. AVER-ELL, OF NEW YORK, N. Y., ASSIGNOB 'I'O JOHN CHATILLON 82; SONS,

OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SPRING SCALE Application filed June 6, 1929.

This invention relates to scales, and more particularly to scales or balances of the spring type.

Spring balance scales as heretofore made have been rendered inaccurate because of the longitudinal expansion or contraction of the wire of the spring due to changes in temper ture and to changes in stiffness of the springs also due to changes in temperature which caused such scales to inaccurately register the weight of commodities weighed thereon. These two causes combine to produce a multiplication of error in the reading of the scale, causing them to under-indicate at low temperatures and over-indicate at high temperatures.

In the manufacture of spring scales of a theoreticallycorrect standard, it is not only necessary to provide means for correcting for the so-called changes of stiffness of the spring, but also for correcting the zero point.

Accordingly, a primary object of the present invention is to provide a spring scale which will automatically correct the indicater for the zero point as well as substantially compensate through the indicator for the varying stiffness of the springs due to changes in temperature. That is to say, it is proposed to provide a spring scale including means, preferably a single element, for correcting the reading of the indicator for the changing length of the wire of the spring, and for substantially compensating for the errors of the indicator due to the changes in the stiffness of thespring due to changes in temperature.

The inaccuracy of springs due to temperature is caused by the increase or decrease in length of the wire of the spring which affects the zero point and a change in the stifiness of the spring which does not substantially affect the zero point but does affect the read ing on the scale. The error of the zero reading of the indicator is constant at any given temperature at all loads but the indicator error due to change of stiffness of the spring increases approximately in direct proportion to the load which greatly complicates the problem of producing compensating ele ments to correct both defects and particularly Serial No. 368,852.

where a single element corrects both inacof the construction shown in Fig. i.

Fig. l'is a detail horizontal sectional view taken on the line 4rl of Fig. showing the rack and pinion at the point of engagement.

Similar reference characters designate corresponding parts throughout the several fig ures of the drawings.

As previously indicated, the present invention contemplates the utilization of a simple and practical means, preferably in the form of a single element for automatically correcting the reading of the indicator for the zero point as well as for substantially compensating for the variation in the stiffness of the spring or springs.

To that end I use a novel type of rack for engaging with the pinion on the dial shaft, the material of which the said rack is composed having a very high co-ehicient of expansi on as compared to the co-efficient of expansion of the steel wire of the scale springs.

The problem which confronted me was to find a material for my rack whose coefiicient of expansion was such that it would correct the error in the springs due to changes in the stiffness of the springs caused by changes in temperatures and to pivot such rack on the runner at such a distance below its point of contact with the rack when the scale was uncler no load that the expansion of the rack between the pinion and its pivot would correct the scale reading for the zero point at all temperatures.

I have found that acetate sheet stock manufactured. by The Celluloid Company of America is a suitable material for my rack which will accurately correct the zero reading and substantially compensate for chan in stiffness of the spring. 7

By way of illustrating the general theory of the invention before proceeding to a. more detailed description thereof, attention is directed to Fig. 2 of the drawings wherein certain elements of the scale mechanism are designated for convenience of reference. The runner is designated as A and has mounted thereon a rack, carrier B to which the rack R is pivoted as at C. The runner A is suspended on the springs S which. are sup iorted at the top on a hang-er designated as H and the rack R engages with the pinion P on the shaft of the indicator.

The d'stance for any given settingbetween the center of the pivot C ancL the axis of the pinion P is constant a no load at the temperature for which the rack carrier B is adjusted. It the temperature the length of the wire 0:? the .1? ing will increase which will permit the runner to drop down prop n tionately. This increase in temperature in also cause the sin gle element or rack R 1 has much higher co-etlicicnt of c eam than the wire (it sprin ,9; to expan tain the indicator at zero. In at tion the sin elenumt or racl; has but one ettective movement, that is a movement in the direction of its length as di t nguished twin an expansion movement as well as a bending movement. It the runner is then. subiectcd to a load the stittness of the springs S wil be reduced and they will be flexed hevond the normal. fle-Xure tor the temperature for which the scale was adjusted but the longitudinal expansion of the rack will also auto matically correct the readin e" oi the indicator thereb} 'li'cetin r a correction of the zero reading of the indicator without loading and also suhstanti ally compensate for errors in the readin ot the indicator when the springs are placed under load and this will be true for all loads and all variations ct temperatures.

The detail features ot cmistructio are tullv described and claimed in my (Jo-pending application filed of even date herewith Serial No. 368,856.

Vithout further description it is thought that the features and advantages of the in vcntion will be readih apparent to those skilled in the art. and it will of course he un derstood that changes in the form, proportion and minor details of. construction may he resorted to, without departing from the spirit ot the invention and scope of the EH TDQZNh-Wl claims.

I claim:

1. In a spring scale, the combination of a. load spring, an indicator, operating means for the indicator composed of homogeneous material and extending to both sides of the point of engagement with the indicator wherehv the contraction and expansion longitudinally of the operating means under temperature changes will automatically correct the reading of the indicator for the changing length of the wire of the spring, caused by the changes in temperature, and substantially compensate for changes in the stillness of the spring due to changes in temperature.

2. In a spring scale, the combination of a load spring, a rotatable indicator, indicator operz g means composed of homogeneous material and extending to both sides of its engagement with the rotatable indicator, said operating means having a high coetlieient oi :rpansion for automatically correcting the reading 01 the indicator for the changes in length of the wire of the spring and substan tially compensating for changes in the stiffness of the spring due to changes in temperature,

3. In a spring scale, the combination of a load spring, an indicator, and an indicator operating element composed of homogeneous 1 having a suhsantially higher cocfiicient ol xpansion than the spring of the s ale for automatically correcting the reading of the indicator for the changes in the length of wire in the spring and substantially coinpensating for changes in the stillness of the spring due to changes in temperature.

4;. In a s ing scale, the combination of a load spring, an indicator, anc a single indicater operating element of homo 'encous material extending to both sides oi: the point of engagement oil. said element with the indicator and adapted to opei to to correct the zero reading off: the indicator and substantially compensate for the indicator error due to changes in stiffness of the spring due to temperature.

F In a spring scale, the combination of an indicator, a pinion mounted on a shalt carrying the indicator, a runner suspended on the spring of the scale, a rack composed of homogeneous material so pivoted on said runner and. meshed with said pinion and having such a co-cllicicnt of ex; msion as will opera to the indicator to substantially compensate the reading of the indicator for changes in the length and stitlness ot the springs due to temperature changes.

6. In a spring scale, the comhiat on of a s n-l ng with an indicator and indicator operating means composed of homogeneous material having a higher co-eliicient ot cxpansion than that the spring mater al adapted h its longitudinal expansion and contraction to correct error in the reading of the indicator for changes in length and substantially compensate for errors due to changes in stiffness of the springs due to temperature changes.

In testimony whereof I ac'liz: my signature.

SYLVESlER G. AVE-B illie 

